Brian S Posner - Net Worth and Insider Trading
Brian S Posner Net Worth
The estimated net worth of Brian S Posner is at least $3 Million dollars as of 2026-09-10. Brian S Posner is the Director of Biogen Inc and owns about 7,400 shares of Biogen Inc (BIIB) stock worth over $2 Million. Brian S Posner is the Director of Bioverativ Inc and owns about 6,693 shares of Bioverativ Inc (BIVV) stock worth over $702,631. Brian S Posner is also the Director of Dyne Therapeutics Inc and owns about 24,500 shares of Dyne Therapeutics Inc (DYN) stock worth over $470,033. Besides these, Brian S Posner also holds Arch Capital Group Ltd (ACGL) . Details can be seen in Brian S Posner's Latest Holdings Summary section.
Disclaimer: The insider information is derived from SEC filings. The estimated net worth is based on the final shares held after open market or private purchases and sales of common stock with a transaction code of "P" or "S" on Form 4, assuming that Brian S Posner has not made any transactions after 2026-06-08 and currently still holds the listed stock(s). Please note that this estimate may not reflect the actual net worth.
Transaction Summary of Brian S Posner
Brian S Posner Insider Ownership Reports
Based on ownership reports from SEC filings, as the reporting owner, Brian S Posner owns 6 companies in total, including Biogen Inc (BIIB) , Arch Capital Group Ltd (ACGL) , and Bioverativ Inc (BIVV) among others .
Click here to see the complete history of Brian S Posner’s form 4 insider trades.
Insider Ownership Summary of Brian S Posner
| Ticker | Company | Transaction Date | Type of Owner |
|---|---|---|---|
| BIIB | Biogen Inc | 2021-06-04 | director |
| ACGL | Arch Capital Group Ltd | 2026-06-03 | director |
| BIVV | Bioverativ Inc | 2018-03-08 | director |
| 2014-06-03 | director | ||
| 2006-08-01 | other: Pres. & CEO & CoCIO of SubAdvis | ||
| 2026-06-08 | director |
Brian S Posner Latest Holdings Summary
Brian S Posner currently owns a total of 4 stocks. Among these stocks, Brian S Posner owns 7,400 shares of Biogen Inc (BIIB) as of June 4, 2021, with a value of $2 Million and a weighting of 57.08%. Brian S Posner owns 6,693 shares of Bioverativ Inc (BIVV) as of August 9, 2017, with a value of $702,631 and a weighting of 25.72%. Brian S Posner also owns 24,500 shares of Dyne Therapeutics Inc (DYN) as of June 8, 2026, with a value of $470,033 and a weighting of 17.2%. The other 1 stocks Arch Capital Group Ltd (ACGL) have a combined weighting of 0% among all his current holdings.
Latest Holdings of Brian S Posner
| Ticker | Company | Latest Transaction Date | Shares Owned | Current Price ($) | Current Value ($) |
|---|---|---|---|---|---|
| BIIB | Biogen Inc | 2021-06-04 | 7,400 | 210.73 | 1,559,402 |
| BIVV | Bioverativ Inc | 2017-08-09 | 6,693 | 104.98 | 702,631 |
| DYN | Dyne Therapeutics Inc | 2026-06-08 | 24,500 | 19.19 | 470,033 |
| ACGL | Arch Capital Group Ltd | 2026-06-03 | 0 | 96.12 | 0 |
Holding Weightings of Brian S Posner
Brian S Posner Form 4 Trading Tracker
According to the SEC Form 4 filings, Brian S Posner has made a total of 0 transactions in Biogen Inc (BIIB) over the past 5 years. The most-recent trade in Biogen Inc is the sale of 360 shares on June 4, 2021, which brought Brian S Posner around $98,701.
According to the SEC Form 4 filings, Brian S Posner has made a total of 0 transactions in Bioverativ Inc (BIVV) over the past 5 years. The most-recent trade in Bioverativ Inc is the acquisition of 1,000 shares on August 9, 2017, which cost Brian S Posner around $59,190.
According to the SEC Form 4 filings, Brian S Posner has made a total of 7 transactions in Dyne Therapeutics Inc (DYN) over the past 5 years, including 7 buys and 0 sells. The most-recent trade in Dyne Therapeutics Inc is the acquisition of 2,000 shares on June 8, 2026, which cost Brian S Posner around $33,880.
More details on Brian S Posner's insider transactions can be found in the Insider Trading History of Brian S Posner table.Insider Trading History of Brian S Posner
* The information on this page (including Insider Trading Shares, Share Changes, Cost, etc.) is sourced exclusively from Form 4 filings and does not incorporate any data from 13F or 13D/G filings. As a result, it may differ from the values shown on the Guru page.
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Brian S Posner Trading Performance
GuruFocus tracks the stock performance after each of Brian S Posner's buying transactions within different timeframes. To be detailed, the average return of stocks after 3 months bought by Brian S Posner is 17.95%. GuruFocus also compares Brian S Posner's trading performance to market benchmark return within the same time period. The performance of stocks bought by Brian S Posner within 3 months outperforms 14 times out of 18 transactions in total compared to the return of S&P 500 within the same period.
You can select different timeframes to see how Brian S Posner's insider trading performs compared to the benchmark.
Performance of Brian S Posner
Brian S Posner Ownership Network
Ownership Network List of Brian S Posner
Ownership Network Relation of Brian S Posner

Brian S Posner Owned Company Details
What does Biogen Inc do?
Who are the key executives at Biogen Inc?
Brian S Posner is the director of Biogen Inc. Other key executives at Biogen Inc include Head of Pharm Ops and Tech Nicole Murphy , Head of Development Priya Singhal , and Head of Global Product Strat. Rachid Izzar .
Biogen Inc (BIIB) Insider Trades Summary
Over the past 18 months, Brian S Posner made no insider transaction in Biogen Inc (BIIB). Other recent insider transactions involving Biogen Inc (BIIB) include a net sale of 7,731 shares made by Priya Singhal , a net sale of 2,223 shares made by Rachid Izzar , and a net purchase of 1,235 shares made by Caroline Dorsa .
In summary, during the past 3 months, insiders sold 1,186 shares of Biogen Inc (BIIB) in total and bought 0 shares, with a net sale of 1,186 shares. During the past 18 months, 11,140 shares of Biogen Inc (BIIB) were sold and 1,238 shares were bought by its insiders, resulting in a net sale of 9,902 shares.
Biogen Inc (BIIB)'s detailed insider trading history can be found in Insider Trading Tracker table.
Biogen Inc Insider Transactions
Brian S Posner Mailing Address
Above is the net worth, insider trading, and ownership report for Brian S Posner. Based on the public information released on the U.S. Securities and Exchange Commission (SEC) website, Brian S Posner's mailing address is: Cambridge Ma 02142.